Aftertreatment devices like catalytic converter assemblies are widely known and available for use with diesel engines. Often, a unique catalytic converter assembly may be required for use with each original equipment manufacturer because each original equipment manufacturer utilizes a unique chassis. These assemblies include aftertreatment devices such as that disclosed in U.S. Pat. No. 5,031,401 to Hinderks.
Many assemblies have a housing and a catalyst coated substrate retained inside of the housing. The housing typically includes an inlet for permitting exhaust gases to enter the housing wherein they pass through the substrate and exit out through an outlet. The housing typically protects the catalyst coated substrate and directs exhaust gases to flow through the catalyst coated substrate. The catalyst's purpose is to catalyze chemical reactions with exhaust gases in order to reduce emissions content. The catalyst materials are typically coated on a flow-through honeycomb-type substrate. The substrate provides an opportunity for exhaust gases to interact with the catalyst and may be of any of a number of known materials such as a cordierite ceramic material or a metal foil material. However, it should be appreciated that the specific choice of materials and type of substrate is determined by the specific emissions performance desired and is dependent upon the particular engine used in combination with the catalyst.
As exhaust gases flow past a catalyst coated substrate a phenomenon known as plugging may occur. Plugging is when certain portions of the exhaust gases accumulate on the catalyst. Over time, the accumulation can continue to build up to the extent that flow of exhaust gases across portions of a catalytic coated substrate may be precluded. Therefore, it may be desirable to fairly evenly distribute the flow of exhaust gases across the catalyst coated substrate.
Additionally, it is desirable to pass as hot of exhaust gases as possible across catalyst coated substrates in order to utilize the additional heat during the catalytic reduction process. Hotter exhaust gases are also less likely to cause as much plugging as cooler exhaust gases. Therefore, it may be beneficial to mount the catalytic converter assembly directly to the exhaust manifold of an engine, thereby reducing heat lost by exhaust gases prior to flowing across the catalyst coated substrate. Mounting the catalytic converter assembly directly to the exhaust manifold also facilitates using the same converter assembly for many different original equipment manufacturers.
However, known assemblies fail to bring exhaust gases into a housing, turn the exhaust gases quickly, balance flow variances and evenly distribute flow of exhaust gases across the catalyst coated substrate in a manner which achieves optimal emissions reduction. Prior systems use complex control systems or rely on precise port sizing and geometric relationships to achieve distribution of the exhaust gases across the catalyst coated substrate. When used over engines with multiple ratings and having multiple operating conditions the many various components, intricacies of the structural members, and complexity of the exhaust gas flows may increase manufacturing and design costs as well as increase maintenance and other owning and operating costs.